1. In marketroid-speak, superior; implies a
product imbued with exclusive magic by the unmatched brilliance of the
company's own hardware or software designers.

2. In the language of hackers and users, inferior; implies a product
not conforming to open-systems standards, and thus one that puts the
customer at the mercy of a vendor able to gouge freely on service and
upgrade charges after the initial sale has locked the customer in. Often
used in the phrase “proprietary crap”.

3. Synonym for closed-source or non-free, e.g. software issued
without license rights permitting the public to independently review,
develop and redistribute it.

Proprietary software should be distinguished from commercial
software. It is possible for software to be commercial (that is, intended
to make a profit for the producers) without being proprietary. The
reverse is also possible, for example in binary-only freeware.